HSC Survey Results

Scots Bay Survey # 8 Results from 11/08/2024

Survey Details

4 commercial purse seiners conducted this fishing survey on 11/08/2024 starting at 20:00:00, which was 2.67 hours after hide tide.

All vessels ran two transects each in the Main Survey Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Melissa.

A total of 194 tags were applied during the survey over 1 event(s) from 2024-08-12 to 2024-08-12 from 1 vessel(s).

Samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Margaretsville NS, Station #315m Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for Scots Bay using standardized parallel transects is 15,213mt, and with turnover applied 10,296mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2024-08-11 19:35:58 2024-08-11 22:27:39 -65.235 45.061 -64.779 45.216 SB 39.92 7.53
BP T02 2024-08-11 22:45:52 2024-08-12 00:44:45 -64.805 45.261 -65.218 45.120 SB 36.07 9.83
C1 T01 2024-08-11 19:42:04 2024-08-11 22:49:30 -65.235 45.072 -64.727 45.245 SB 46.03 7.96
C1 T02 2024-08-11 23:08:03 2024-08-12 01:42:26 -64.787 45.282 -65.237 45.129 SB 40.31 8.46
LM T01 2024-08-11 19:25:25 2024-08-11 22:32:21 -65.236 45.049 -64.695 45.226 SB 47.32 8.20
LM T02 2024-08-11 22:50:19 2024-08-12 01:35:05 -64.756 45.265 -65.233 45.103 SB 41.93 8.24
MS T01 2024-08-11 19:41:27 2024-08-11 22:49:52 -65.215 45.043 -64.746 45.196 SB 42.89 7.37
MS T02 2024-08-11 23:10:35 2024-08-12 01:43:28 -64.772 45.244 -65.229 45.090 SB 41.33 8.76

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
LM T02 -35.5 -48.090 0.055
MS T02 -35.5 -48.114 0.055
C1 T01 -35.5 -49.240 0.042
C1 T02 -35.5 -50.631 0.031
BP T02 -35.5 -51.184 0.027
BP T01 -35.5 -52.867 0.018
MS T01 -35.5 -53.838 0.015
LM T01 -35.5 -54.758 0.012
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
Main Box -35.5 480 -50.4863 0.0318 15,213 100 NA 2,920 19.19
Northern Box NA 0 NA NA NA 0 NA NA NA
Eastern Box NA 0 NA NA NA 0 NA NA NA

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by C1, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by LM, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
Scots Bay 1 2024-05-05 78,662 78,662 2023-05-22 40,856 40,856 47,629 47,629
Scots Bay 2 2024-05-20 29,842 17,255 2023-06-06 113,767 108,783 98,582 92,772
Scots Bay 3 2024-06-02 93,804 89,523 2023-06-18 34,279 15,158 29,417 12,720
Scots Bay 4 2024-06-16 33,347 22,278 2023-07-02 11,745 5,113 9,330 3,622
Scots Bay 5 2024-07-01 7,252 3,123 2023-07-16 19,283 17,575 17,387 16,022
Scots Bay 6 2024-07-15 4,539 3,560 2023-07-30 4,550 1,904 3,474 1,093
Scots Bay 7 2024-07-29 32,655 32,016 2023-08-13 4,299 3,616 2,777 2,247
Scots Bay 8 2024-08-11 15,213 10,296 2023-08-27 2,897 2,300 1,612 1,224
Scots Bay 9 NA NA NA 2023-09-10 3,054 2,916 3,219 0
Scots Bay 10 NA NA NA 2023-09-24 3,420 2,997 2,318 0
Scots Bay 11 NA NA NA 2023-10-09 3,388 2,971 2,521 0
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 Scots Bay 241,538 204,189 218,266 177,329
2024 Scots Bay 295,314 256,713 NA NA

Tagging, Plankton, and CTD Data

Summary map

Vessel Tags
Lady Melissa 194

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Melissa Lady Melissa
Set Number SB2024-13 SB2024-14
Ground SB SB
Date 11/08/2024 11/08/2024
Wind Direction (km/h) SW SW
Swell (m) 0 0
Air Temp (c) 22 22
Tow Details
Tow Start 18:29:00 18:45:00
Tow End 18:39:00 18:55:00
Start Lat 45.05450 45.04833
End Lat 45.06817 45.05233
Start Lon -65.24683 -65.21817
End Lon -65.2315 -65.2090
Avg Tow Depth (m) 2.961977 6.705542
Speed 6.5 5.4
Heading 37 129
Tide Direction with against
Other Data Collection
Flow Start 293541 293541
Flow End 357632 357632
No. Revolutions 64091 64091
Distance (m) 1722.317 1722.317
Volume 5410.66 5410.66
Secchi Disappear (m) 7 7
Secchi Reappear (m) 8 8

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is SB2024-13, which was with the tide and had an average depth of 2.9619767m. The second tow is SB2024-14, which was against the tide and had an average depth of 6.7055417m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 Scots Bay surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for Scots Bay.

Vessel Performance

Speed

Average vessel speed was 8.29. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

More than 2km of distance was cut from the planned lines; vessels are reminded to complete their assigned lines straight and without deviating or cutting corners short.